Plates and bodies to be applied on iron tools and machine members



[Patented Apr. 27, i9

bodies to m'rns Armhomes To an APPL moN rooLsANnMAcmNn men or:

Heinrich Friedrich August Liibbe, deceased, late,

of Berlin Germany, by Ottilie Liibbe, ad ministratrix, Berlin, Germany;

and Erich Kruppa,,Berlin, Germany; vested in the Alien Property Custodian I No Application February 7,1941, Se-

rial N0. 377,846. 1939 and machine members which are'particularly exposed to wear may berendered resistant'to wear and tear by brazing on to these surfaces, forinstance; plates or other bodies made of hard metal or metal alloy or by building up-a layer of such alloys resistant to wear, such as,'metal carbides or stellite-like alloys.

Plates or shaped bodies entirely made of sintered hard metal alloys have, as it is known, only a low coeflicient of thermal expansion as compared with other metals. This peculiarity of the hard metal alloys requires great care and skill in the preparation of workpieces provided with such plates. Tools or machine members of normal construction and also certain kinds of alloyed steel which are exposed to a high thermal strain are oftenunsuitable for being coated with plates of hard metal alloys. In order to avoid tension cracks, the plates of hard metal alloys must be brazed with great care and only by trained work-.- men. The mean coefflcient of thermal expansion within a'temperature range from 20 C. to 100 C. amounts, for instance, in the case of a carbon steel to about 1110-, and in the case of a hardmetal alloy of the class known as cemented carbides having for instance the composition of 88% of tungsten, 6% of cobalt and 6% of carbon to only 5.10-. Considering the intermediate layer formed by brazing and the coemcient of thermal expansion of the copper preferably used in this case with 1'7.10-, the path'of the thermal curve is very, unfavorable. Moreover, when building up hard metal alloys on workpieces of small thickness, for instance, the contact surfaces of many measuring instruments, distortions easily occur.

These drawbacks of the knownprocesses are avoided, according to the present invention,- by

3 Claims. (01. -136) ally by at least one intermediate layer obtained ermany February 11,

by' the formation of mixed crystals, by alloyinr or by diffusion.

Suitable plates and shapes are, for instance 3 those composed of the following metals, the order being from the outside to the inside: tungsten carbide/mixed crystals/iron, or tungsten carbide/mixed crystals/cobalt, in case the metal of the' workpiece is' a. carbon steel; or chromium/mixed crystals/carbon steel in case the metal of the workpiece is an alloyed steel, for instance, of the type used for valves.

The exterior layer or the working surface of plates or shapes prepared according to the present invention may eonsist of any suitable metal or a, corresponding metal mixture. Preferably there are used hard metals alloys of known composition with or without addition of auxiliary metals of low melting point. Furthermore, heavy I metals of high melting point and compounds thereof can be used either alone, mixed with each other or in admixture with metals of low melting point as well as stellite-like alloys.

As fixing layers there are especially suitable metals with which the metals of the outer layl:

' form alloys or mixed crystals. Preferably there iixing'on the workpieces plates or shapes which 1 consist of at least one outer layer of a. metal or a metal alloy resistant to wear and at least one that'of the metal of the workpiece. For the fixing layers there is suitably chosen-a, metal or' metal alloy whose ceemcient of thermal expansion lies betweenthat of the support metal and that of the metal alloys of the outer layers which are fast to wear. Outer layers and fixing layers .are combined to a solid inseparable body genermetal of the fixing layers being equal to or near are used metals of the iron group, that is to say, cobalt, nickel or the alloys thereof, as well as carbon steel or alloyed steel.

The outer layer resistant to wear may be con nected to the fixing'layers in one of the various ways known per se. Thus, the outer layer may be melted on to the fixing layers, for instance, by autogenous or electric building up or sintering. In the latter case the pulverized metals are advantageously pressed on to a plate f e fixin layer which plate is roughened on the side next to the outer layer resistant-to wear. It is, how ever, also possible to flrst compress the fixing layer of, for instance, pulverized iron, cobalt, nickel or the like or the alloys thereof,: to press thereon the pulverimd metal or metal alloy of the outer layer resistant to wear and then to sinter the whole body.

Instead oi one single fixing layer there may also be used several such layers, the content of hard metal alloy diminishing gradually from the outer layer to the support. This may be accomplished Icy-adding to the, pulverized metal of the tering of three zones: outer layer resistant to wear/layer of mixed crystals/fixing layer is tion, may be fixed on a tool or a machine membet in various ways. If the parts are to be united by welding; the tool and the plates are heated in a furnace to red heat, a suitable weldz'ng powder is strewn on the surface of the work- .piece and the plate to be fixed is placed thereon. The body is then heated to white heat and the intimate union is eilected bya slight pressure or stroke. The body is advantageously cooled in ashes or pulverized'c'oal.

Plates and tools may' also 'be' combined by electric resistance welding or the soft fixing layer carrying the hard metal may be fixed to the tool by screws. The application of dovetailed grooves in the fixing layer and shrinking-on of the'plates thus formed to the tool are'aiso possible. I

eel-mac l of the metal used'for the trough'is very low and --in contradistlnction to the prescription of the present invention-is nearly equal to that of the metal used for cutting tools. Moreover. plates and trough are not combined to a solid, inseparable body by a layer formed by mixed crystals or the like according to the idea underlying this inventlon.'

efllcient of thermal expansion of the diflerent layers of the plate and the workpiece proper whereby a tool of long lifeis obtained.

We claim: v

1. Plates and bodies for application to iron tools and machine members, said plates and Tools thus prepared may be cautiously hardened or annealed without detrimental effect on theouter layer of the plate, said layer being in most cases a naturally hard body.

It has already been proposed-to insert between the plate consisting throughout of hard metal and the workpiece a thick-walled trough of a relatively hard and tough metal into which the plate is brazed. This trough is intended to protect the plate against unfavorable mechanical influences and detrimental tensions which may be caused by the influence of heat, not only by bodies consisting of an outer metallic layer of cemented carbides, an inner layer of a metal having a coeflicient of expansion approximating thatof the tools and machine members, and an intermediate layer operating to permanently unite the inner and outer layers and comprising mixed crystals of the metals of the outer and inner layers resulting from the direct surfacediflusion or -a lloying of the metals of the inner and outer layers.

2. Articles as defined in claim 1 wherein the inner layer is of a metalv of the iron group.

3. Articles as defined in claim 1 wherein the inner layer is of a metal of the iron group and the outer layer is ofcemented tungsten carbide.

. o'rrnmLiinBE, Administratria: of IIeinrich. Friedrich August Lilbbe, Deceased.

ERICK KRUPPA. 

